Solar control coatings having a layer stack of glass/Si3N4/NiCr/Si3N4 are known, where the metallic NiCr layer is the sole infrared (IR) reflecting layer in the coating. In certain instances, the NiCr layer may be nitrided. For example, see U.S. Pat. No. 5,688,585. Unfortunately, while such layer stacks with NiCr IR reflecting layers provide efficient solar control and are overall good coatings, they sometimes are lacking in terms of: (a) corrosion resistance to acid (e.g., HCl boil); (b) mechanical performance such as scratch resistance; and/or (c) color stability upon heat treatment for tempering, heat bending, or the like (i.e., too high of ΔE* value(s)). For example, a known heat treatable coated article having a layer stack of glass/Si3N4/NiCr/Si3N4 has rather high glass side reflective ΔE* value above 5.0 after heat treatment (HT) at 625 degrees C. for about ten minutes. This high glass side reflective ΔE* value means that the coated article when HT will not approximately match its non-HT counterpart with respect to glass side reflective color after such HT.
A recent development by one of the current inventors, set forth in U.S. 2004/0214013 (hereby incorporated herein by reference), is the use of a layer stack of glass/Si3N4/NbZrOx/Si3N4, where the NbZrOx is used as the IR reflecting layer in the coating. This layer stack is advantageous with respect to the aforesaid glass/Si3N4/NiCr/Si3N4 layer stack in that coated articles with the NbZrOx IR reflecting layer realize improved color stability upon heat treatment (i.e., lower ΔE* values) and/or improved durability.
While coated articles having a layer stack of glass/Si3N4/NbZrOx/Si3N4 represent improvements in the art, it would be desirable in certain example instances if even lower ΔE* values could be achieved.
Furthermore, solar control coatings such as those mentioned above often do not block significant amounts of ultraviolet (UV) radiation. In other words, such coatings typically provide only moderate or negligible UV protection, since the materials used in the layer stacks are transparent for short wavelengths (e.g., below 400 nm). Thus, even when such coatings are provided on windows such as IG windows or the like, significant amounts of UV radiation makes its way through the window and into the building or other interior space. UV radiation is penetration tends to damage furniture and other elements inside of buildings or the like.
Materials such as vanadium oxide and cerium oxide absorb significant amounts of UV radiation. However, while such materials are characterized by a very steep onset of absorption for UV radiation, the onset of radiation absorption occurs in significant part in the visible part of the spectrum thereby leading to a significant distortion of colors when look through such a coating (e.g., a yellow shift). Accordingly, viewing characteristics tend to be degraded when layers of such materials are used.
In view of the above, it will be appreciated that there exists a need in the art for a coated article including a solar control coating which is capable of blocking at some UV radiation in an efficient manner. Certain example embodiments of this invention relate to a coated article which permits significant UV absorption properties to be achieved.
In certain example embodiments of this invention, it has surprisingly been found that the provision of a layer consisting essentially of, or comprising, zirconium silicon oxynitride (e.g., ZrSiOxNy) unexpectedly improves blocking (reflecting and/or absorption) of UV radiation in a manner which does not significantly degrade other optical properties of a coated article such as visible transmission and/or color. Moreover, as an added unexpected advantage, it has surprisingly been found that the provision of a layer(s) of zirconium silicon oxynitride (e.g., ZrSiOxNy) unexpectedly improves (lowers) ΔE* values upon heat treatment, thereby permitting a coated article when heat treated (HT) to more closely match its non-HT counterpart with respect to glass side reflective color after such HT.
In certain example embodiments of this invention, a layer of zirconium silicon oxynitride may be tuned in a manner so as to achieve a desired amount of UV blocking and/or absorption. It has been found that zirconium silicon oxynitride has optical constants (n and k) which allow adjustment of the onset of absorption by varying oxygen content of the layer for example. Moreover, it has been found that zirconium silicon oxynitride has a refractive index (n) in a range which is very adaptable to solar control coatings, so that such layer(s) may be used in solar control coatings without significantly changing the visible appearance of the coated article or certain performance data. Thus, in certain example embodiments of this invention, the absorption edge of the curve defined by a layer of zirconium silicon oxynitride can be adjusted by changing the oxygen content thereof, which may be done for example by adjusting the amount of oxygen introduced into the sputtering chamber(s) during reactive sputter-deposition of the layer. In particular, for example, as oxygen content of the layer increases, the absorption edge of the curve defined by the layer of zirconium silicon oxynitride moves toward lower wavelengths away from certain visible wavelengths. Thus, in certain example embodiments, a balancing or tuning can be performed so as to achieve a desired balance between visible transmission and UV absorption.
In certain example embodiments of this invention, there is provided a coated article for use in a window and including a coating supported by a substrate, the coating comprising: an infrared (IR) reflecting layer; and a layer comprising zirconium silicon oxynitride located over at least the IR reflecting layer. In certain example embodiments of this invention, the IR reflecting layer comprises one or more of: (a) an oxide of niobium zirconium; (b) a nitride of niobium zirconium; (c) a nitride of nickel chromium; (d) substantially metallic nickel chromium; and (e) niobium.
In other example embodiments, there is provided a coated article including a coating supported by a glass substrate, the coating comprising: a first dielectric layer; an infrared (IR) reflecting layer located on the substrate over at least the first dielectric layer; and a layer comprising zirconium silicon oxynitride located on the substrate over at least the IR reflecting layer and the first dielectric layer.